Brochure

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2.
Thermostats
Table 6: Contact system and application
Switch type - single pole double throw
Switch action
Application
Terminals 1 – 4 close high and open low
Terminals 1 – 2 can be used as low temperature alarm
Low pressure cut-out
Terminals 1 – 2 open high and close low
Terminals 1 – 4 can be used as high temperature alarm
High pressure cut-out
Setting
Pressure switches
Cut-in and cut-out pressures of the system should always be checked with an accurate pressure gauge.
Pressure setting for switches with automatic reset.
Set the cut-out pressure on RANGE scale and dierential on DIFF scale.

NOTE:
Restart pressure is equal to cut-out pressure minus dierential value.
Pressure switches with manual reset
Set the cut-out pressure on the RANGE scale. Pressure limiters can be manually reset by pressing reset button when
the pressure is equal to the cut-out pressure minus xed value of the dierential.
Thermostats
Thermostats with automatic reset
Set the cut-out temperature on the RANGE scale and dierential on the DIFF scale. Restart temperature is equal to
the cut-out temperature minus dierential value.
 NOTE:
The dierential scale is only a reference. The exact value of distances on the scale depends on where in its range the
switch cut-in is set. Use the dierential scale as a guide, and if precise function is required, establish the dierential
setting by comparing function with an accurate thermometer in the controlled zone.
Thermostats with manual reset
Set the cut-out temperature on the range scale.
The dierential is xed. Restart the system by pressing the reset button after the temperature of the sensor falls to a
value equal to the range scale setting minus the xed dierential.
Terminology
Pressure switches
Set point
A predetermined value to which a switch is adjusted and at which it performs its intended function.
Reset:
Manual reset: Units with manual reset can only be restored to operational mode by activation of the external
reset button.
Automatic reset: Units with automatic reset is restored to operational mode automatically.
Maximum working pressure
The maximum permissible pressure for safe functioning of a heating system or any of its part.
Snap function
A specic contact force is maintained until snap is initiated. The time over which contact force reaches zero is a few
milliseconds; therefore, contact bounce cannot occur as a result, for example, of slight vibrations before cut-out. The
snap-action contact system will continue to function even when micro-welds are created between the contacts
during cut-in. The force created to separate the contacts is strong, and instantly shears o all contact surface welds
© Danfoss | Climate Solutions | 2021.02 AI209986438809en-000602 | 5
Pressure switches and thermostats, Type KP